code: def test_fastface_backbones_registry():
      backbones = FACE_DETECTION_BACKBONES.available_keys()
      assert "lffd_slim" in backbones
      assert "lffd_original" in backbones
  
      backbone, _ = FACE_DETECTION_BACKBONES.get("lffd_original")(
          pretrained=False
      )
      assert isinstance(backbone, LFFD)
  
file_path: lightning-flash/tests/image/face_detection/test_model.py
imports: import contextlib
  from unittest.mock import patch
  import flash
  import pytest
  from flash.__main__ import main
  from flash.core.registry import FlashRegistry
  from flash.core.utilities.imports import _FASTFACE_AVAILABLE
  from flash.image import FaceDetectionData, FaceDetector
label_desc: Use image node_id 2 for calling a global function with example usage: test_fastface_backbones_registry() without return types